-LRB- CNN -RRB- -- American journalist James Foley was murdered , beheaded by an English-speaking member of ISIS , the extremist group that calls itself the Islamic State and has already conquered large swaths of two Middle Eastern countries . The sickening execution , recorded and released online for the world to see , came with a warning to the U.S. : ISIS showed another captive American journalist , believed to be Steven Sotloff , and threatened to kill him too if the U.S. does not stop helping those fighting to stop ISIS advances .

The killing and the threat , along with all the evidence ISIS is leaving as it gouges its way across the region , are a direct challenge to the American people , to the U.S. government and to the international community .

As it makes increasingly clear what kind of an organization it is , ISIS is sending a message : `` Stay out of this , so we can keep driving toward our objective . ''

President Obama said Wednesday that `` We will do everything we can to protect our people ... The entire world is appalled by the brutal murder . ''

The U.S. government has crucial steps to take now . First , obviously , it can not give into ISIS threats and must continue helping dislodge ISIS from northern Iraq where it is engaging in ethnic cleansing against Christians and other minorities ; kidnapping , raping and selling women ; and massacring people . The U.S. effort should keep a special focus on helping America 's loyal and ideologically moderate friends , the Kurds of Iraq .

At the same time , the U.S. should make a strong diplomatic push to obtain international legitimacy for the campaign to defeat ISIS . It is important to prevent ISIS from scoring a recruiting victory among Muslims and anti-Western and anti-American camps by portraying this as a war between Islam and the West , which it is not .

There are few people on Earth who are not horrified by ISIS . That includes the overwhelming majority of Muslims . The grand mufti of Saudi Arabia , Abdul Aziz al-Sheikh , called ISIS and al Qaeda `` Enemy No. 1 '' of Islam . Countless Muslims have criticized and condemned them .

ISIS is the enemy of anyone who does not belong to ISIS . They kill minorities , Shiite Muslims and Sunnis who do n't abide by their views . They are virulently opposed to the West , to the U.S. , to modernity and to anyone who sees the world differently from their narrow medieval perspective .

The U.S. should seek a U.N. resolution declaring that the international community , including the Muslim world , considers ISIS and its methods repugnant . Any country that disagrees , any government that is not revolted by ISIS and troubled by its methods and its goals , should go on record saying so .

Before ISIS , we knew that human beings are capable of unspeakable brutality . But anyone who thought man 's inhumanity to man had eased after the mass crimes of the 20th century now knows better . ISIS did n't just remind us how cruel humans can be ; it has taken the use of brutality as a weapon of intimidation , extermination , genocide and recruitment propaganda to new levels .

ISIS is not the first to murder victims in large numbers ; it is not the first to kill those who disagree with its beliefs or who belong to different ethnic or religious groups . But it seems no group has advertised its bloodlust with such relish and effectiveness .

More important , those using these methods , embracing this philosophy , are in control of enormous territories . When ISIS calls itself a state , it is not hyperbole by very much . ISIS has taken over a a tract of land bigger than many countries , something that al Qaeda , its comparatively mild-mannered inspiration , never came close to achieving .

ISIS has established and gained full dominion not only of cities and populations but of wealthy oil-producing lands . It is now financially self-sufficient , collecting millions of dollars every day from oil smuggling operations . If not stopped , it could continue its push toward the oil fields of southern Iraq at the edge of the Persian Gulf , which remains the epicenter of oil and gas production that allows the global economy to function .

If Osama bin Laden were n't dead , he would die of envy .

ISIS views the videos of mass executions , of severed heads on poles and of crucified men , as a way to keep its enemies frightened and weakened , and a way to tell prospective recruits that it is fearless in its war to create an Islamic caliphate ruling over all the world 's Muslims . Its leader , Abu Bakr al-Baghdadi , incidentally , claims to rule over all Muslims and believes the ultimate goal of ISIS is to take over huge sections of Asia , Europe and Africa .

The killing of Foley , an idealistic journalist , sharpens our understanding of the organization seeking to dominate the Middle East . That the man who murdered him might have been British should erase any remaining fantasy in the West that this gruesome war , now raging in Syria and Iraq , will stay within any country 's or any region 's borders .

Those who seek to downplay the risk to the United States should think again .

Britain has confirmed that Foley 's killer was most likely a British citizen . There have been reports of hundreds , even thousands , of Europeans training , fighting and killing alongside ISIS .

In June 2013 , a video from Syria surfaced , showing men cutting off another man 's head . To the shock of Europeans , they were heard speaking Dutch .

The ISIS members who hold European passports are able to travel freely across Europe and the U.S. and are prepared to do the unthinkable . There are hundreds of Germans , Spaniards , Belgians , French . Graduates of the Syria war , from where ISIS pushed into Iraq , have killed in Europe .

And ISIS ideology is gaining support in the continent . Last month , ISIS flags flew in an anti-Israel demonstration in the Hague , chanting against America and the West and most enthusiastically , `` Death to the Jews . ''

ISIS can simply not be allowed to keep a foothold in the Middle East . If it does , the consequences will become even more catastrophic . In Iraq alone , 1.2 million people have been displaced , thousands killed .

It is politically and strategically complicated , because ISIS is also fighting Syrian President Bashar al-Assad and Hezbollah , and defeating ISIS would also be enormously pleasing to Iran . But the group is a growing threat .

The strategy of supporting the Kurds and the Iraqis in the front lines is a good one . It must be bolstered with material and diplomatic support . If it proves insufficient to turning back the bloody ISIS tide , then it must be revamped .

Foley 's mother said her son gave his life trying to expose to the world the suffering of the Syrian people . That suffering has now extended to Iraq , and it will only become more widespread if ISIS is not stopped .

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Frida Ghitis : U.S. can not give in to ISIS threats , must focus on helping Kurds of Iraq

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Ghitis : U.N. resolution should declare that Muslims , rest of the world find ISIS horrific

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Ghitis : U.S. should make sure this is not framed as a war against Islam and the West

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She says ISIS is a threat to the whole world ; Europeans are joining in big numbers